Hooking up my 3000 w inverter

hankgoldhankgold Registered Users Posts: 1
I have  a Solar hookup in my Travel trailer, Have a 1200 w inverter, , has been grounded to the frame, and the AC connection runs to a Separate Panel box.  with 15 Am fuses , to separate plugs.  Now i`m installing a new Aims 3000 W inverter, Is it ok to hook up neg to frame the same way.  I have a100 AM, Circuit Breaker on positive link. to inverter. thanks 

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,994 admin
    Welcome to the forum Hank,

    Generally, heavy battery / off grid power applications run both + and - leads from the battery bank to the point of use.

    The battery negative bus is tied to frame ground via (at least) a 6 AWG cable. The point of use (such as the AC inverter case) is also connected to frame ground of the vehicle... Grounds are intended to only pass fault current (i.e., a short circuit from + AC inverter to chassis, passes back through the two frame ground back to the battery--And causes the DC fuse/breaker to the inverter to trip).

    Car devices (starter, auto radio, etc.) most times only have a positive lead running to them, and use the motor/frame ground for the negative lead.

    I am a little confused as to which method you are following for wiring... Note that body panels/motors/etc. are typically insulated by rubber bushings/motor mounts/etc. for sound/vibration control. And there are ground straps that "bypass" these mounts to make sure there is a viable/heavy current return path (folks with HAM radios in vehicles, frequently have to add bonding straps all over the place to reduce RF interference).

    The other question... If this is a 3,000 Watt AC inverter on a 12 volt battery bus... That is almost too large of inverter to run at rated power and have reasonable size copper cables and battery bank. For example, a 3kW inverter should have a fuse/breaker/branch circuit rating of:
    • 3,000 Watts * 1/0.85 AC inverter eff * 1/10.5 volt battery cutoff * 1.25 NEC current derating = 420 Amp circuit wiring suggested on a 12 volt battery
    And you would need a Flooded Cell Lead Acid battery bank of >~1,200 AH @ 12 volts to supply that amount of current for a significant amount of time (hour or more).

    Generally, for a travel trailer, they have a much smaller battery bank (around 200-400 AH @ 12 volt) and a 500-1,000 Watt AC inverter (suggested maximum) is about it...

    If you need to support larger loads, generally a genset is cheaper and will supply those power levels with just a few gallons of gasoline vs close to a 800 lbs of FLA batteries (a ~1,200 AH @ 12 volt battery bank).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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